1. Field of the Invention
The present invention is related to optical systems and components, and in particular to optical systems with integrated optical components.
2. Background Information
A typical optical network includes transceivers, amplifiers, multiplexers and demultiplexers, amplifiers, switches and other components. Each transmitting portion of a transceiver converts an electrical signal to an optical signal and launches the optical signal into an optical fiber. A multiplexer combines the individual optical signals from each optical fiber into a multiple channel optical signal and launches the multiple channel optical signal into an optical fiber. A demultiplexer separates the channels out of the multiple-channel optical signal and launches them into separate fibers. Then each receiving portion of a transceiver accepts an optical signal from a fiber and converts it to an electric signal.
Currently, optical network components are discrete components in that each component performs a single function and is connected by optical fibers to other components. For example, an arrayed waveguide grating (AWG) multiplexer/demultiplexer is produced on one separate integrated circuit (or chip).
Erbium doped fiber amplifiers (EDFA) are also large and bulky subsystems composed of discrete components (the spool of erbium-doped optical fiber, laser to produce pump light, circulators to prevent light back-reflection, fiber combiners to combine pump light and signal light, and other components).
In recent years, erbium doped waveguide amplifiers (EDWA), i.e., discrete amplifiers on chip, have been fabricated as described in “8-mW Threshold Er3+-Doped Planar Waveguide Amplifier,” by Ruby N. Gosh, et al., published in IEEE Photonics Technology Letters, Vol. 8, No. 4, April 1996, as described in “Integrate Planar Waveguide Amplifier with 15 dB gain at 1550 nm,” by J. Shmulovich, et al., in Optical Fiber Communications '99 Technical Digest Post-deadline Paper PD-42, San Diego, Calif., 1999, or as described in “Erbium-doped silica-based waveguide amplifier integrated with a 980/1530 nm WDM coupler,” by K. Hattori, et al., published in Electronic Letters, Vol. 30, No. 11, May 26, 1994.
The optical network components described above are usually interconnected using optical fiber and fiber connectors. Fiber-to-component interfaces and fiber connectors contribute to optical signal power loss, which causes the need to install even more amplifiers to keep the signal above the noise level. Moreover, with numerous discrete components, the installation, test, reconfiguration of networks is becoming prohibitively difficult and expensive.